Copper electroplating bath

Abstract

A copper electroplating bath useful in filling non-through holes formed on a substrate which contains a water-soluble copper salt, sulfuric acid, and chloride ions and further contains a brightener, a carrier, and a leveler as additives, wherein the leveler contains at least one water-soluble polymer containing quaternary nitrogen, tertiary nitrogen, or both which are cationizable in a solution. In the copper electroplating bath, the filling power for non-through holes formed on a substrate can be easily controlled so as to fit to the size of the holes only by changing the quaternary nitrogen to tertiary nitrogen ratio of the water-soluble polymer to be used as the leveler, which enables copper electroplating of non-through holes of various sizes with a good fit to the sizes.

The invention claimed is: 
     
       1. An electrolytic copper plating bath used for filling blind via holes formed on a substrate with copper, wherein the electrolytic copper plating bath consists of a water-soluble salt, sulfuric acid and chloride ions, and, as additives, a brightener, a carrier and a leveler, wherein said leveler consists of a copolymer (B) represented by the following formula (9): 
       
         
           
           
               
               
           
         
       
       wherein R 21  and R 22 , respectively, represent an unsubstituted alkyl group having 1 to 4 carbon atoms, R 23  represents a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, and r and s are, respectively, an integer of 1 or more. 
     
     
       2. The electrolytic copper plating bath as defined in  claim 1 , characterized in that a quaternary nitrogen to tertiary nitrogen ratio in said leveler is controlled depending on a hole diameter and an aspect ratio (hole depth/hole diameter) of intended blind via holes. 
     
     
       3. The electrolytic copper plating bath as defined in  claim 1 , characterized in that said brightener is made of a sulfur additive selected from those of the following formulas (1) to (4): 
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2  and R 3 , respectively, represent an alkyl group having 1 to 5 carbon atoms, M represents a hydrogen atom or an alkali metal, a is an integer of 1 to 8, and b, c and d are, respectively, 0 or 1, and said carrier is made of a polyalkylene glycol represented by the following formula (5):
   HO—(R 4 —O) e —H  (5)
 
 wherein R 4  represents an alkylene group having 2 or 3 carbon atoms and e is an integer of 4 or more. 
 
     
     
       4. The electrolytic copper plating bath as defined in  claim 3 , characterized in that said brightener is made of a sulfur additive selected from those of the formula (2). 
     
     
       5. The electrolytic copper plating bath as defined in  claim 4 , characterized in that said brightener is bis-(3-sodium sulfopropyl)disulfide. 
     
     
       6. The electrolytic copper plating bath as defined in  claim 1 , characterized in that a hole diameter of said blind via holes ranges 1 to 150 μm and an aspect ratio (hole depth/hole diameter) ranges 0.3 to 1.5.